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=head1 NAME |
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Coro - real threads in perl |
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1.1 |
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=head1 SYNOPSIS |
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use Coro; |
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async { |
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# some asynchronous thread of execution |
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print "2\n"; |
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cede; # yield back to main |
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print "4\n"; |
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}; |
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print "1\n"; |
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cede; # yield to coroutine |
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print "3\n"; |
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cede; # and again |
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# use locking |
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use Coro::Semaphore; |
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my $lock = new Coro::Semaphore; |
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my $locked; |
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$lock->down; |
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$locked = 1; |
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$lock->up; |
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1.1 |
=head1 DESCRIPTION |
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This module collection manages coroutines, that is, cooperative |
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threads. Coroutines are similar to kernel threads but don't (in general) |
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run in parallel at the same time even on SMP machines. The specific flavor |
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of coroutine used in this module also guarantees you that it will not |
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switch between coroutines unless necessary, at easily-identified points |
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in your program, so locking and parallel access are rarely an issue, |
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making coroutine programming much safer and easier than using other thread |
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models. |
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Unlike the so-called "Perl threads" (which are not actually real threads |
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but only the windows process emulation ported to unix), Coro provides a |
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full shared address space, which makes communication between coroutines |
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very easy. And coroutines are fast, too: disabling the Windows process |
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emulation code in your perl and using Coro can easily result in a two to |
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four times speed increase for your programs. |
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Coro achieves that by supporting multiple running interpreters that share |
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data, which is especially useful to code pseudo-parallel processes and |
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for event-based programming, such as multiple HTTP-GET requests running |
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concurrently. See L<Coro::AnyEvent> to learn more on how to integrate Coro |
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into an event-based environment. |
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In this module, a coroutines is defined as "callchain + lexical variables |
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+ @_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own |
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callchain, its own set of lexicals and its own set of perls most important |
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global variables (see L<Coro::State> for more configuration and background |
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info). |
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See also the C<SEE ALSO> section at the end of this document - the Coro |
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module family is quite large. |
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1.8 |
=cut |
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package Coro; |
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use strict qw(vars subs); |
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no warnings "uninitialized"; |
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|
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use Coro::State; |
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use base qw(Coro::State Exporter); |
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|
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our $idle; # idle handler |
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our $main; # main coroutine |
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our $current; # current coroutine |
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|
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our $VERSION = "5.0"; |
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|
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our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub); |
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our %EXPORT_TAGS = ( |
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prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], |
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); |
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our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready)); |
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|
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=head1 GLOBAL VARIABLES |
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=over 4 |
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=item $Coro::main |
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|
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This variable stores the coroutine object that represents the main |
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program. While you cna C<ready> it and do most other things you can do to |
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coroutines, it is mainly useful to compare again C<$Coro::current>, to see |
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whether you are running in the main program or not. |
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|
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=cut |
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# $main is now being initialised by Coro::State |
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|
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=item $Coro::current |
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|
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The coroutine object representing the current coroutine (the last |
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coroutine that the Coro scheduler switched to). The initial value is |
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C<$Coro::main> (of course). |
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This variable is B<strictly> I<read-only>. You can take copies of the |
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value stored in it and use it as any other coroutine object, but you must |
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not otherwise modify the variable itself. |
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|
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=cut |
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sub current() { $current } # [DEPRECATED] |
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|
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=item $Coro::idle |
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|
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This variable is mainly useful to integrate Coro into event loops. It is |
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usually better to rely on L<Coro::AnyEvent> or LC<Coro::EV>, as this is |
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pretty low-level functionality. |
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This variable stores a callback that is called whenever the scheduler |
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finds no ready coroutines to run. The default implementation prints |
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"FATAL: deadlock detected" and exits, because the program has no other way |
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to continue. |
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|
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This hook is overwritten by modules such as C<Coro::Timer> and |
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C<Coro::AnyEvent> to wait on an external event that hopefully wake up a |
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coroutine so the scheduler can run it. |
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Note that the callback I<must not>, under any circumstances, block |
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the current coroutine. Normally, this is achieved by having an "idle |
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coroutine" that calls the event loop and then blocks again, and then |
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readying that coroutine in the idle handler. |
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See L<Coro::Event> or L<Coro::AnyEvent> for examples of using this |
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technique. |
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|
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Please note that if your callback recursively invokes perl (e.g. for event |
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handlers), then it must be prepared to be called recursively itself. |
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|
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=cut |
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$idle = sub { |
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require Carp; |
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Carp::croak ("FATAL: deadlock detected"); |
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}; |
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|
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# this coroutine is necessary because a coroutine |
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# cannot destroy itself. |
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our @destroy; |
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our $manager; |
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$manager = new Coro sub { |
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1.57 |
while () { |
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Coro::_cancel shift @destroy |
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while @destroy; |
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&schedule; |
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} |
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}; |
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$manager->{desc} = "[coro manager]"; |
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$manager->prio (PRIO_MAX); |
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1.43 |
=back |
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1.8 |
|
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1.234 |
=head1 SIMPLE COROUTINE CREATION |
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|
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=over 4 |
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=item async { ... } [@args...] |
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|
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Create a new coroutine and return it's coroutine object (usually |
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unused). The coroutine will be put into the ready queue, so |
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it will start running automatically on the next scheduler run. |
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The first argument is a codeblock/closure that should be executed in the |
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coroutine. When it returns argument returns the coroutine is automatically |
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terminated. |
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The remaining arguments are passed as arguments to the closure. |
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See the C<Coro::State::new> constructor for info about the coroutine |
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environment in which coroutines are executed. |
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|
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Calling C<exit> in a coroutine will do the same as calling exit outside |
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the coroutine. Likewise, when the coroutine dies, the program will exit, |
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just as it would in the main program. |
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|
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If you do not want that, you can provide a default C<die> handler, or |
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simply avoid dieing (by use of C<eval>). |
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Example: Create a new coroutine that just prints its arguments. |
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1.13 |
async { |
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print "@_\n"; |
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} 1,2,3,4; |
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1.8 |
=cut |
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1.13 |
sub async(&@) { |
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my $coro = new Coro @_; |
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$coro->ready; |
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$coro |
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1.8 |
} |
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|
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=item async_pool { ... } [@args...] |
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Similar to C<async>, but uses a coroutine pool, so you should not call |
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terminate or join on it (although you are allowed to), and you get a |
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coroutine that might have executed other code already (which can be good |
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or bad :). |
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On the plus side, this function is about twice as fast as creating (and |
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destroying) a completely new coroutine, so if you need a lot of generic |
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coroutines in quick successsion, use C<async_pool>, not C<async>. |
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|
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The code block is executed in an C<eval> context and a warning will be |
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issued in case of an exception instead of terminating the program, as |
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C<async> does. As the coroutine is being reused, stuff like C<on_destroy> |
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will not work in the expected way, unless you call terminate or cancel, |
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which somehow defeats the purpose of pooling (but is fine in the |
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exceptional case). |
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|
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1.181 |
The priority will be reset to C<0> after each run, tracing will be |
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disabled, the description will be reset and the default output filehandle |
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gets restored, so you can change all these. Otherwise the coroutine will |
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be re-used "as-is": most notably if you change other per-coroutine global |
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1.204 |
stuff such as C<$/> you I<must needs> revert that change, which is most |
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simply done by using local as in: C<< local $/ >>. |
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|
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1.204 |
The idle pool size is limited to C<8> idle coroutines (this can be |
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adjusted by changing $Coro::POOL_SIZE), but there can be as many non-idle |
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coros as required. |
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1.105 |
|
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If you are concerned about pooled coroutines growing a lot because a |
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1.133 |
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool |
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{ terminate }> once per second or so to slowly replenish the pool. In |
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1.232 |
addition to that, when the stacks used by a handler grows larger than 32kb |
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(adjustable via $Coro::POOL_RSS) it will also be destroyed. |
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1.105 |
|
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=cut |
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our $POOL_SIZE = 8; |
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1.232 |
our $POOL_RSS = 32 * 1024; |
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1.134 |
our @async_pool; |
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1.105 |
|
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sub pool_handler { |
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while () { |
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1.134 |
eval { |
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1.227 |
&{&_pool_handler} while 1; |
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1.105 |
}; |
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1.134 |
|
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1.227 |
warn $@ if $@; |
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1.106 |
} |
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} |
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1.105 |
|
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1.181 |
=back |
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|
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1.234 |
=head1 STATIC METHODS |
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|
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1.234 |
Static methods are actually functions that implicitly operate on the |
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current coroutine. |
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1.181 |
|
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=over 4 |
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1.8 |
=item schedule |
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1.6 |
|
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1.181 |
Calls the scheduler. The scheduler will find the next coroutine that is |
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to be run from the ready queue and switches to it. The next coroutine |
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to be run is simply the one with the highest priority that is longest |
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in its ready queue. If there is no coroutine ready, it will clal the |
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C<$Coro::idle> hook. |
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Please note that the current coroutine will I<not> be put into the ready |
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queue, so calling this function usually means you will never be called |
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again unless something else (e.g. an event handler) calls C<< ->ready >>, |
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thus waking you up. |
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This makes C<schedule> I<the> generic method to use to block the current |
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coroutine and wait for events: first you remember the current coroutine in |
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a variable, then arrange for some callback of yours to call C<< ->ready |
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>> on that once some event happens, and last you call C<schedule> to put |
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yourself to sleep. Note that a lot of things can wake your coroutine up, |
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1.196 |
so you need to check whether the event indeed happened, e.g. by storing the |
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1.181 |
status in a variable. |
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1.91 |
|
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1.224 |
See B<HOW TO WAIT FOR A CALLBACK>, below, for some ways to wait for callbacks. |
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1.1 |
|
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1.22 |
=item cede |
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1.1 |
|
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1.181 |
"Cede" to other coroutines. This function puts the current coroutine into |
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the ready queue and calls C<schedule>, which has the effect of giving |
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up the current "timeslice" to other coroutines of the same or higher |
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priority. Once your coroutine gets its turn again it will automatically be |
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resumed. |
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|
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This function is often called C<yield> in other languages. |
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1.7 |
|
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1.102 |
=item Coro::cede_notself |
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|
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1.181 |
Works like cede, but is not exported by default and will cede to I<any> |
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coroutine, regardless of priority. This is useful sometimes to ensure |
302 |
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progress is made. |
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1.102 |
|
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1.40 |
=item terminate [arg...] |
305 |
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1.7 |
|
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1.92 |
Terminates the current coroutine with the given status values (see L<cancel>). |
307 |
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1.13 |
|
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1.141 |
=item killall |
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|
310 |
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Kills/terminates/cancels all coroutines except the currently running |
311 |
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one. This is useful after a fork, either in the child or the parent, as |
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usually only one of them should inherit the running coroutines. |
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|
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1.181 |
Note that while this will try to free some of the main programs resources, |
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1.196 |
you cannot free all of them, so if a coroutine that is not the main |
316 |
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1.181 |
program calls this function, there will be some one-time resource leak. |
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|
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1.1 |
=cut |
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|
320 |
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1.141 |
sub killall { |
321 |
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for (Coro::State::list) { |
322 |
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$_->cancel |
323 |
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if $_ != $current && UNIVERSAL::isa $_, "Coro"; |
324 |
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} |
325 |
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} |
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|
327 |
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1.8 |
=back |
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|
329 |
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1.234 |
=head1 COROUTINE OBJECT METHODS |
330 |
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1.8 |
|
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1.181 |
These are the methods you can call on coroutine objects (or to create |
332 |
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them). |
333 |
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1.6 |
|
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1.8 |
=over 4 |
335 |
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|
336 |
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1.13 |
=item new Coro \&sub [, @args...] |
337 |
root |
1.8 |
|
338 |
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1.181 |
Create a new coroutine and return it. When the sub returns, the coroutine |
339 |
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1.40 |
automatically terminates as if C<terminate> with the returned values were |
340 |
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1.181 |
called. To make the coroutine run you must first put it into the ready |
341 |
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queue by calling the ready method. |
342 |
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1.13 |
|
343 |
root |
1.145 |
See C<async> and C<Coro::State::new> for additional info about the |
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coroutine environment. |
345 |
root |
1.89 |
|
346 |
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1.6 |
=cut |
347 |
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|
348 |
root |
1.225 |
sub _terminate { |
349 |
root |
1.13 |
terminate &{+shift}; |
350 |
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} |
351 |
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|
352 |
root |
1.92 |
=item $success = $coroutine->ready |
353 |
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1.1 |
|
354 |
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1.181 |
Put the given coroutine into the end of its ready queue (there is one |
355 |
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queue for each priority) and return true. If the coroutine is already in |
356 |
|
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the ready queue, do nothing and return false. |
357 |
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|
358 |
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This ensures that the scheduler will resume this coroutine automatically |
359 |
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once all the coroutines of higher priority and all coroutines of the same |
360 |
|
|
priority that were put into the ready queue earlier have been resumed. |
361 |
root |
1.1 |
|
362 |
root |
1.92 |
=item $is_ready = $coroutine->is_ready |
363 |
root |
1.90 |
|
364 |
root |
1.196 |
Return whether the coroutine is currently the ready queue or not, |
365 |
root |
1.28 |
|
366 |
root |
1.92 |
=item $coroutine->cancel (arg...) |
367 |
root |
1.28 |
|
368 |
root |
1.92 |
Terminates the given coroutine and makes it return the given arguments as |
369 |
root |
1.103 |
status (default: the empty list). Never returns if the coroutine is the |
370 |
|
|
current coroutine. |
371 |
root |
1.28 |
|
372 |
|
|
=cut |
373 |
|
|
|
374 |
|
|
sub cancel { |
375 |
pcg |
1.59 |
my $self = shift; |
376 |
root |
1.103 |
|
377 |
|
|
if ($current == $self) { |
378 |
root |
1.226 |
terminate @_; |
379 |
root |
1.103 |
} else { |
380 |
root |
1.226 |
$self->{_status} = [@_]; |
381 |
root |
1.103 |
$self->_cancel; |
382 |
|
|
} |
383 |
root |
1.40 |
} |
384 |
|
|
|
385 |
root |
1.229 |
=item $coroutine->schedule_to |
386 |
|
|
|
387 |
|
|
Puts the current coroutine to sleep (like C<Coro::schedule>), but instead |
388 |
|
|
of continuing with the next coro from the ready queue, always switch to |
389 |
|
|
the given coroutine object (regardless of priority etc.). The readyness |
390 |
|
|
state of that coroutine isn't changed. |
391 |
|
|
|
392 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
393 |
|
|
uses for this one. |
394 |
|
|
|
395 |
|
|
=item $coroutine->cede_to |
396 |
|
|
|
397 |
|
|
Like C<schedule_to>, but puts the current coroutine into the ready |
398 |
|
|
queue. This has the effect of temporarily switching to the given |
399 |
|
|
coroutine, and continuing some time later. |
400 |
|
|
|
401 |
|
|
This is an advanced method for special cases - I'd love to hear about any |
402 |
|
|
uses for this one. |
403 |
|
|
|
404 |
root |
1.208 |
=item $coroutine->throw ([$scalar]) |
405 |
|
|
|
406 |
|
|
If C<$throw> is specified and defined, it will be thrown as an exception |
407 |
root |
1.222 |
inside the coroutine at the next convenient point in time. Otherwise |
408 |
|
|
clears the exception object. |
409 |
|
|
|
410 |
|
|
Coro will check for the exception each time a schedule-like-function |
411 |
|
|
returns, i.e. after each C<schedule>, C<cede>, C<< Coro::Semaphore->down |
412 |
root |
1.223 |
>>, C<< Coro::Handle->readable >> and so on. Most of these functions |
413 |
|
|
detect this case and return early in case an exception is pending. |
414 |
root |
1.208 |
|
415 |
|
|
The exception object will be thrown "as is" with the specified scalar in |
416 |
|
|
C<$@>, i.e. if it is a string, no line number or newline will be appended |
417 |
|
|
(unlike with C<die>). |
418 |
|
|
|
419 |
|
|
This can be used as a softer means than C<cancel> to ask a coroutine to |
420 |
|
|
end itself, although there is no guarantee that the exception will lead to |
421 |
|
|
termination, and if the exception isn't caught it might well end the whole |
422 |
|
|
program. |
423 |
|
|
|
424 |
|
|
You might also think of C<throw> as being the moral equivalent of |
425 |
|
|
C<kill>ing a coroutine with a signal (in this case, a scalar). |
426 |
|
|
|
427 |
root |
1.92 |
=item $coroutine->join |
428 |
root |
1.40 |
|
429 |
|
|
Wait until the coroutine terminates and return any values given to the |
430 |
root |
1.143 |
C<terminate> or C<cancel> functions. C<join> can be called concurrently |
431 |
root |
1.181 |
from multiple coroutines, and all will be resumed and given the status |
432 |
|
|
return once the C<$coroutine> terminates. |
433 |
root |
1.40 |
|
434 |
|
|
=cut |
435 |
|
|
|
436 |
|
|
sub join { |
437 |
|
|
my $self = shift; |
438 |
root |
1.103 |
|
439 |
root |
1.142 |
unless ($self->{_status}) { |
440 |
root |
1.103 |
my $current = $current; |
441 |
|
|
|
442 |
root |
1.142 |
push @{$self->{_on_destroy}}, sub { |
443 |
root |
1.103 |
$current->ready; |
444 |
|
|
undef $current; |
445 |
|
|
}; |
446 |
|
|
|
447 |
|
|
&schedule while $current; |
448 |
root |
1.40 |
} |
449 |
root |
1.103 |
|
450 |
root |
1.142 |
wantarray ? @{$self->{_status}} : $self->{_status}[0]; |
451 |
root |
1.31 |
} |
452 |
|
|
|
453 |
root |
1.101 |
=item $coroutine->on_destroy (\&cb) |
454 |
|
|
|
455 |
|
|
Registers a callback that is called when this coroutine gets destroyed, |
456 |
|
|
but before it is joined. The callback gets passed the terminate arguments, |
457 |
root |
1.181 |
if any, and I<must not> die, under any circumstances. |
458 |
root |
1.101 |
|
459 |
|
|
=cut |
460 |
|
|
|
461 |
|
|
sub on_destroy { |
462 |
|
|
my ($self, $cb) = @_; |
463 |
|
|
|
464 |
root |
1.142 |
push @{ $self->{_on_destroy} }, $cb; |
465 |
root |
1.101 |
} |
466 |
|
|
|
467 |
root |
1.92 |
=item $oldprio = $coroutine->prio ($newprio) |
468 |
root |
1.31 |
|
469 |
root |
1.41 |
Sets (or gets, if the argument is missing) the priority of the |
470 |
root |
1.92 |
coroutine. Higher priority coroutines get run before lower priority |
471 |
|
|
coroutines. Priorities are small signed integers (currently -4 .. +3), |
472 |
root |
1.41 |
that you can refer to using PRIO_xxx constants (use the import tag :prio |
473 |
|
|
to get then): |
474 |
root |
1.31 |
|
475 |
|
|
PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN |
476 |
|
|
3 > 1 > 0 > -1 > -3 > -4 |
477 |
|
|
|
478 |
|
|
# set priority to HIGH |
479 |
|
|
current->prio(PRIO_HIGH); |
480 |
|
|
|
481 |
|
|
The idle coroutine ($Coro::idle) always has a lower priority than any |
482 |
|
|
existing coroutine. |
483 |
|
|
|
484 |
root |
1.92 |
Changing the priority of the current coroutine will take effect immediately, |
485 |
|
|
but changing the priority of coroutines in the ready queue (but not |
486 |
root |
1.31 |
running) will only take effect after the next schedule (of that |
487 |
root |
1.92 |
coroutine). This is a bug that will be fixed in some future version. |
488 |
root |
1.31 |
|
489 |
root |
1.92 |
=item $newprio = $coroutine->nice ($change) |
490 |
root |
1.31 |
|
491 |
|
|
Similar to C<prio>, but subtract the given value from the priority (i.e. |
492 |
|
|
higher values mean lower priority, just as in unix). |
493 |
|
|
|
494 |
root |
1.92 |
=item $olddesc = $coroutine->desc ($newdesc) |
495 |
root |
1.41 |
|
496 |
|
|
Sets (or gets in case the argument is missing) the description for this |
497 |
root |
1.208 |
coroutine. This is just a free-form string you can associate with a |
498 |
|
|
coroutine. |
499 |
root |
1.150 |
|
500 |
root |
1.208 |
This method simply sets the C<< $coroutine->{desc} >> member to the given |
501 |
|
|
string. You can modify this member directly if you wish. |
502 |
root |
1.150 |
|
503 |
root |
1.41 |
=cut |
504 |
|
|
|
505 |
|
|
sub desc { |
506 |
|
|
my $old = $_[0]{desc}; |
507 |
|
|
$_[0]{desc} = $_[1] if @_ > 1; |
508 |
|
|
$old; |
509 |
root |
1.8 |
} |
510 |
root |
1.1 |
|
511 |
root |
1.233 |
sub transfer { |
512 |
|
|
require Carp; |
513 |
|
|
Carp::croak ("You must not call ->transfer on Coro objects. Use Coro::State objects or the ->schedule_to method. Caught"); |
514 |
|
|
} |
515 |
|
|
|
516 |
root |
1.8 |
=back |
517 |
root |
1.2 |
|
518 |
root |
1.234 |
=head1 GLOBAL FUNCTIONS |
519 |
root |
1.92 |
|
520 |
|
|
=over 4 |
521 |
|
|
|
522 |
root |
1.97 |
=item Coro::nready |
523 |
|
|
|
524 |
|
|
Returns the number of coroutines that are currently in the ready state, |
525 |
root |
1.181 |
i.e. that can be switched to by calling C<schedule> directory or |
526 |
|
|
indirectly. The value C<0> means that the only runnable coroutine is the |
527 |
|
|
currently running one, so C<cede> would have no effect, and C<schedule> |
528 |
|
|
would cause a deadlock unless there is an idle handler that wakes up some |
529 |
|
|
coroutines. |
530 |
root |
1.97 |
|
531 |
root |
1.103 |
=item my $guard = Coro::guard { ... } |
532 |
|
|
|
533 |
root |
1.119 |
This creates and returns a guard object. Nothing happens until the object |
534 |
root |
1.103 |
gets destroyed, in which case the codeblock given as argument will be |
535 |
|
|
executed. This is useful to free locks or other resources in case of a |
536 |
|
|
runtime error or when the coroutine gets canceled, as in both cases the |
537 |
|
|
guard block will be executed. The guard object supports only one method, |
538 |
|
|
C<< ->cancel >>, which will keep the codeblock from being executed. |
539 |
|
|
|
540 |
|
|
Example: set some flag and clear it again when the coroutine gets canceled |
541 |
|
|
or the function returns: |
542 |
|
|
|
543 |
|
|
sub do_something { |
544 |
|
|
my $guard = Coro::guard { $busy = 0 }; |
545 |
|
|
$busy = 1; |
546 |
|
|
|
547 |
|
|
# do something that requires $busy to be true |
548 |
|
|
} |
549 |
|
|
|
550 |
|
|
=cut |
551 |
|
|
|
552 |
|
|
sub guard(&) { |
553 |
|
|
bless \(my $cb = $_[0]), "Coro::guard" |
554 |
|
|
} |
555 |
|
|
|
556 |
|
|
sub Coro::guard::cancel { |
557 |
|
|
${$_[0]} = sub { }; |
558 |
|
|
} |
559 |
|
|
|
560 |
|
|
sub Coro::guard::DESTROY { |
561 |
|
|
${$_[0]}->(); |
562 |
|
|
} |
563 |
|
|
|
564 |
|
|
|
565 |
root |
1.92 |
=item unblock_sub { ... } |
566 |
|
|
|
567 |
|
|
This utility function takes a BLOCK or code reference and "unblocks" it, |
568 |
root |
1.181 |
returning a new coderef. Unblocking means that calling the new coderef |
569 |
|
|
will return immediately without blocking, returning nothing, while the |
570 |
|
|
original code ref will be called (with parameters) from within another |
571 |
|
|
coroutine. |
572 |
root |
1.92 |
|
573 |
root |
1.124 |
The reason this function exists is that many event libraries (such as the |
574 |
root |
1.92 |
venerable L<Event|Event> module) are not coroutine-safe (a weaker form |
575 |
|
|
of thread-safety). This means you must not block within event callbacks, |
576 |
root |
1.181 |
otherwise you might suffer from crashes or worse. The only event library |
577 |
|
|
currently known that is safe to use without C<unblock_sub> is L<EV>. |
578 |
root |
1.92 |
|
579 |
|
|
This function allows your callbacks to block by executing them in another |
580 |
|
|
coroutine where it is safe to block. One example where blocking is handy |
581 |
|
|
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to |
582 |
root |
1.181 |
disk, for example. |
583 |
root |
1.92 |
|
584 |
|
|
In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when |
585 |
|
|
creating event callbacks that want to block. |
586 |
|
|
|
587 |
root |
1.181 |
If your handler does not plan to block (e.g. simply sends a message to |
588 |
|
|
another coroutine, or puts some other coroutine into the ready queue), |
589 |
|
|
there is no reason to use C<unblock_sub>. |
590 |
|
|
|
591 |
root |
1.183 |
Note that you also need to use C<unblock_sub> for any other callbacks that |
592 |
|
|
are indirectly executed by any C-based event loop. For example, when you |
593 |
|
|
use a module that uses L<AnyEvent> (and you use L<Coro::AnyEvent>) and it |
594 |
|
|
provides callbacks that are the result of some event callback, then you |
595 |
|
|
must not block either, or use C<unblock_sub>. |
596 |
|
|
|
597 |
root |
1.92 |
=cut |
598 |
|
|
|
599 |
|
|
our @unblock_queue; |
600 |
|
|
|
601 |
root |
1.105 |
# we create a special coro because we want to cede, |
602 |
|
|
# to reduce pressure on the coro pool (because most callbacks |
603 |
|
|
# return immediately and can be reused) and because we cannot cede |
604 |
|
|
# inside an event callback. |
605 |
root |
1.132 |
our $unblock_scheduler = new Coro sub { |
606 |
root |
1.92 |
while () { |
607 |
|
|
while (my $cb = pop @unblock_queue) { |
608 |
root |
1.227 |
&async_pool (@$cb); |
609 |
root |
1.105 |
|
610 |
root |
1.227 |
# for short-lived callbacks, this reduces pressure on the coro pool |
611 |
|
|
# as the chance is very high that the async_poll coro will be back |
612 |
|
|
# in the idle state when cede returns |
613 |
|
|
cede; |
614 |
root |
1.92 |
} |
615 |
root |
1.105 |
schedule; # sleep well |
616 |
root |
1.92 |
} |
617 |
|
|
}; |
618 |
root |
1.208 |
$unblock_scheduler->{desc} = "[unblock_sub scheduler]"; |
619 |
root |
1.92 |
|
620 |
|
|
sub unblock_sub(&) { |
621 |
|
|
my $cb = shift; |
622 |
|
|
|
623 |
|
|
sub { |
624 |
root |
1.105 |
unshift @unblock_queue, [$cb, @_]; |
625 |
root |
1.92 |
$unblock_scheduler->ready; |
626 |
|
|
} |
627 |
|
|
} |
628 |
|
|
|
629 |
root |
1.224 |
=item $cb = Coro::rouse_cb |
630 |
|
|
|
631 |
|
|
Create and return a "rouse callback". That's a code reference that, when |
632 |
|
|
called, will save its arguments and notify the owner coroutine of the |
633 |
|
|
callback. |
634 |
|
|
|
635 |
|
|
See the next function. |
636 |
|
|
|
637 |
|
|
=item @args = Coro::rouse_wait [$cb] |
638 |
|
|
|
639 |
|
|
Wait for the specified rouse callback (or the last one tht was created in |
640 |
|
|
this coroutine). |
641 |
|
|
|
642 |
|
|
As soon as the callback is invoked (or when the calback was invoked before |
643 |
|
|
C<rouse_wait>), it will return a copy of the arguments originally passed |
644 |
|
|
to the rouse callback. |
645 |
|
|
|
646 |
|
|
See the section B<HOW TO WAIT FOR A CALLBACK> for an actual usage example. |
647 |
|
|
|
648 |
root |
1.92 |
=back |
649 |
|
|
|
650 |
root |
1.8 |
=cut |
651 |
root |
1.2 |
|
652 |
root |
1.8 |
1; |
653 |
root |
1.14 |
|
654 |
root |
1.224 |
=head1 HOW TO WAIT FOR A CALLBACK |
655 |
|
|
|
656 |
|
|
It is very common for a coroutine to wait for some callback to be |
657 |
|
|
called. This occurs naturally when you use coroutines in an otherwise |
658 |
|
|
event-based program, or when you use event-based libraries. |
659 |
|
|
|
660 |
|
|
These typically register a callback for some event, and call that callback |
661 |
|
|
when the event occured. In a coroutine, however, you typically want to |
662 |
|
|
just wait for the event, simplyifying things. |
663 |
|
|
|
664 |
|
|
For example C<< AnyEvent->child >> registers a callback to be called when |
665 |
|
|
a specific child has exited: |
666 |
|
|
|
667 |
|
|
my $child_watcher = AnyEvent->child (pid => $pid, cb => sub { ... }); |
668 |
|
|
|
669 |
|
|
But from withina coroutine, you often just want to write this: |
670 |
|
|
|
671 |
|
|
my $status = wait_for_child $pid; |
672 |
|
|
|
673 |
|
|
Coro offers two functions specifically designed to make this easy, |
674 |
|
|
C<Coro::rouse_cb> and C<Coro::rouse_wait>. |
675 |
|
|
|
676 |
|
|
The first function, C<rouse_cb>, generates and returns a callback that, |
677 |
|
|
when invoked, will save it's arguments and notify the coroutine that |
678 |
|
|
created the callback. |
679 |
|
|
|
680 |
|
|
The second function, C<rouse_wait>, waits for the callback to be called |
681 |
|
|
(by calling C<schedule> to go to sleep) and returns the arguments |
682 |
|
|
originally passed to the callback. |
683 |
|
|
|
684 |
|
|
Using these functions, it becomes easy to write the C<wait_for_child> |
685 |
|
|
function mentioned above: |
686 |
|
|
|
687 |
|
|
sub wait_for_child($) { |
688 |
|
|
my ($pid) = @_; |
689 |
|
|
|
690 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => Coro::rouse_cb); |
691 |
|
|
|
692 |
|
|
my ($rpid, $rstatus) = Coro::rouse_wait; |
693 |
|
|
$rstatus |
694 |
|
|
} |
695 |
|
|
|
696 |
|
|
In the case where C<rouse_cb> and C<rouse_wait> are not flexible enough, |
697 |
|
|
you can roll your own, using C<schedule>: |
698 |
|
|
|
699 |
|
|
sub wait_for_child($) { |
700 |
|
|
my ($pid) = @_; |
701 |
|
|
|
702 |
|
|
# store the current coroutine in $current, |
703 |
|
|
# and provide result variables for the closure passed to ->child |
704 |
|
|
my $current = $Coro::current; |
705 |
|
|
my ($done, $rstatus); |
706 |
|
|
|
707 |
|
|
# pass a closure to ->child |
708 |
|
|
my $watcher = AnyEvent->child (pid => $pid, cb => sub { |
709 |
|
|
$rstatus = $_[1]; # remember rstatus |
710 |
|
|
$done = 1; # mark $rstatus as valud |
711 |
|
|
}); |
712 |
|
|
|
713 |
|
|
# wait until the closure has been called |
714 |
|
|
schedule while !$done; |
715 |
|
|
|
716 |
|
|
$rstatus |
717 |
|
|
} |
718 |
|
|
|
719 |
|
|
|
720 |
root |
1.17 |
=head1 BUGS/LIMITATIONS |
721 |
root |
1.14 |
|
722 |
root |
1.217 |
=over 4 |
723 |
|
|
|
724 |
root |
1.219 |
=item fork with pthread backend |
725 |
|
|
|
726 |
|
|
When Coro is compiled using the pthread backend (which isn't recommended |
727 |
|
|
but required on many BSDs as their libcs are completely broken), then |
728 |
|
|
coroutines will not survive a fork. There is no known workaround except to |
729 |
|
|
fix your libc and use a saner backend. |
730 |
|
|
|
731 |
root |
1.217 |
=item perl process emulation ("threads") |
732 |
|
|
|
733 |
root |
1.181 |
This module is not perl-pseudo-thread-safe. You should only ever use this |
734 |
|
|
module from the same thread (this requirement might be removed in the |
735 |
|
|
future to allow per-thread schedulers, but Coro::State does not yet allow |
736 |
root |
1.217 |
this). I recommend disabling thread support and using processes, as having |
737 |
|
|
the windows process emulation enabled under unix roughly halves perl |
738 |
|
|
performance, even when not used. |
739 |
|
|
|
740 |
|
|
=item coroutine switching not signal safe |
741 |
|
|
|
742 |
|
|
You must not switch to another coroutine from within a signal handler |
743 |
|
|
(only relevant with %SIG - most event libraries provide safe signals). |
744 |
|
|
|
745 |
root |
1.221 |
That means you I<MUST NOT> call any function that might "block" the |
746 |
root |
1.217 |
current coroutine - C<cede>, C<schedule> C<< Coro::Semaphore->down >> or |
747 |
|
|
anything that calls those. Everything else, including calling C<ready>, |
748 |
|
|
works. |
749 |
|
|
|
750 |
|
|
=back |
751 |
|
|
|
752 |
root |
1.9 |
|
753 |
|
|
=head1 SEE ALSO |
754 |
|
|
|
755 |
root |
1.181 |
Event-Loop integration: L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
756 |
root |
1.152 |
|
757 |
|
|
Debugging: L<Coro::Debug>. |
758 |
|
|
|
759 |
|
|
Support/Utility: L<Coro::Specific>, L<Coro::Util>. |
760 |
root |
1.67 |
|
761 |
root |
1.235 |
Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, |
762 |
|
|
L<Coro::SemaphoreSet>, L<Coro::RWLock>. |
763 |
root |
1.67 |
|
764 |
root |
1.181 |
IO/Timers: L<Coro::Timer>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::AIO>. |
765 |
|
|
|
766 |
root |
1.235 |
Compatibility: L<Coro::LWP> (but see also L<AnyEvent::HTTP> for |
767 |
|
|
a better-working alternative), L<Coro::BDB>, L<Coro::Storable>, |
768 |
|
|
L<Coro::Select>. |
769 |
root |
1.152 |
|
770 |
root |
1.181 |
XS API: L<Coro::MakeMaker>. |
771 |
root |
1.67 |
|
772 |
root |
1.181 |
Low level Configuration, Coroutine Environment: L<Coro::State>. |
773 |
root |
1.1 |
|
774 |
|
|
=head1 AUTHOR |
775 |
|
|
|
776 |
root |
1.66 |
Marc Lehmann <schmorp@schmorp.de> |
777 |
root |
1.64 |
http://home.schmorp.de/ |
778 |
root |
1.1 |
|
779 |
|
|
=cut |
780 |
|
|
|